Here's a link to a demonstration video! GameBoy Color emulation at 60FPS, properly synchronized using the audio. Using a DisplayLink DL-165, a FullHD monitor, a USB audio card and a WiiClassic I²C controller.

Most of the CPU time is taken up by the routine that sends the framebuffer via USB. If that were not there, the CPU load would go down from 60% to about 26%. Which means that there's a lot of things to optimize here yet...

I'll go the 'X11 Xorg server' route for a while and see where that takes me :).